Drive-by-wire lawnmower

ABSTRACT

The mower has at least two independently driven wheels that are each capable of bi-directional rotation. The at least two wheels are independently driven so that operation of the at least two wheels causes the at least two wheels to independently rotate which propels and steers the mower. A microprocessor controls the operation of the at least two wheels in accordance with signals received by the microprocessor. The mower has at least one controller. The at least one controller sends signals to the microprocessor that the microprocessor uses to control the operation of the at least two wheels. The operation of the at least one controller causes the at least two wheels to propel and steer the mower.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.10/017,473 filed on Dec. 14, 2001. The disclosure of the aboveapplication is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to zero turning radius vehicles, such asturf care vehicles, skid steer loaders, and the like, and morespecifically, to riding lawn mowers that are driven-by-wire.

BACKGROUND OF THE INVENTION

Riding lawn mowers come in a variety of sizes and configurations. Thetypical riding lawn mower has an internal combustion engine thatprovides power to propel the riding lawn mower. In some riding lawnmowers, the internal combustion engine is used to turn a hydraulicpump(s) that supplies a flow of hydraulic fluid that is used to drivewheels on the mower. The hydraulically driven wheels propel the mower.The speed at which the mower is propelled can be controlled by adjustingthe rate of flow of the hydraulic fluid to the wheels. The steering ofthe typical riding lawn mower is performed by a steering wheel that ismechanically linked to wheels on the mower. In the case of ahydraulically driven riding lawn mower, the steering can also beaccomplished by adjusting the rate at which wheels on opposite sides ofthe mower rotate so that the wheels rotate at different rates. The ratesat which the wheels rotate is controlled by adjusting the flow rate ofthe hydraulic fluid to the wheels. The adjusting of the flow rate cancause the wheels to rotate at different speeds and the mower to steer inthe direction of the wheel that is rotating at the lower speed.

The typical hydraulically driven riding lawn mower uses a variety ofmechanical linkages to control the speed of the mower and to steer themower. The mechanical linkages are operated by a user of the mower. Theuser manipulates the mechanical linkages to cause the mower to bepropelled and to control the direction in which the mower travels. Forexample, a steering wheel can be rotated to control the direction inwhich the wheels are oriented so that the direction in which the mowermoves can be controlled. Levers can be mechanically linked to valves tocontrol the operation of the valves. The levers are linked so thatmovement of the levers causes the valves to adjust the volume anddirection of the flow of hydraulic fluid to each of the hydraulicallydriven wheels. The adjustment of the volume of flow of hydraulic fluidto each of the wheels controls the speed at which the wheels rotate. Thelevers can be manipulated so that a different volume of hydraulic fluidflows to each of the hydraulically driven wheels and each wheel rotatesat a different speed relative to each other which controls the directionin which the mower travels. The adjustment of the direction of the flowof hydraulic fluid to each of the wheels controls the direction in whichthe wheels rotate and whether the riding lawn mower is propelled in aforward or backward direction.

While the use of mechanical linkages to control the operation of atypical riding lawn mower with hydraulically driven wheels has proveduseful, the use of mechanical linkages has drawbacks. For example,adjustments to the control and operation of the lawn mower can bedifficult and time consuming. The mechanical linkages may need to beadjusted in length or connected to different attachment points so thecontrol and operation of the mower can be adjusted. Additionally, due tosafety concerns about where a person adjusting the mechanical linkagesneeds to place their hands, some adjustments cannot be made while themower is operating. Therefore, the results of the adjustments of themechanical linkages cannot be ascertained until after the mower is inoperation again. This can result in an iterative process of starting andstopping the mower and adjusting the mechanical linkages until thedesired operation is achieved which may be a long and exhaustiveprocess. Furthermore, it is not always feasible to use mechanicallinkages to provide a complex or highly adjustable control scheme forthe riding lawn mower. The operation of the mechanical linkages needs tobe easy to understand and operate by a user of the mower. As a result,the mechanical linkages are limited to simple and easy movements thatfacilitate the control and operation of the mower and complex controlschemes are difficult to make and may not be feasible to be used by auser of the mower.

Therefore, what is needed is a riding lawn mower that has a controlscheme that allows for improved control of the mower while being easy touse and adjust. Such a control scheme should be intuitive to use andallow for adjustments of the controls during the operation of the mower.Furthermore, it would be advantageous if the control scheme wereconducive to operation of the mower by a user with physical handicaps.

SUMMARY OF THE INVENTION

The present invention is directed to a riding lawn mower that has theabove desired advantageous control scheme. The present invention isdirected to an apparatus for providing a riding lawn mower that isdriven-by-wire. In one preferred embodiment, the drive-by-wire ridinglawn mower has at least two independently driven wheels that are capableof bi-directional rotation. The at least two wheels are independentlydriven so that operation of the at least two wheels causes the at leasttwo wheels to independently rotate. The independent rotation of the atleast two wheels propels and steers the mower. A microprocessor controlsthe operation of the at least two wheels in accordance with signalsreceived by the microprocessor. The mower has at least one controller.The at least one controller sends signals to the microprocessor that themicroprocessor uses to control the operation of the at least two wheelsso that operation of the at least one controller causes the at least twowheels to propel and steer the mower.

Optionally, but preferably, the at least two wheels are hydraulicallydriven and the mower further comprises at least one hydraulic pump thatprovides a flow of hydraulic fluid to drive the at least two wheels. Atleast one proportional servo valve can be provided that controls adirection and speed of the flow of hydraulic fluid to the at least twowheels. The at least one valve is controlled by a microprocessor andadjusts the flow of hydraulic fluid to the at least two wheels inresponse to signals received from the microprocessor. The adjusting ofthe flow of hydraulic fluid by the at least one valve controls thedirection and speed of rotation of the at least two wheels so that themower can be propelled and steered. Even more preferably, the at leastone hydraulic pump is one of a plurality of hydraulic pumps. A firsthydraulic pump of the plurality hydraulic pumps provides a flow ofhydraulic fluid to the first wheel of the at least two wheels. A secondhydraulic pump of the plurality hydraulic pumps provides a flow ofhydraulic fluid to a second wheel of the at least two wheels. The atleast one proportional servo valve is one of a plurality of servovalves. A first valve of the plurality of valves adjusts the flow ofhydraulic fluid from the first hydraulic pump to the first wheel inresponse to signals received from the microprocessor and a second valveof the plurality of valves adjusts the flow of hydraulic fluid from thesecond hydraulic pump to the second wheel in response to signalsreceived from the microprocessor.

Optionally, the mower can further comprise a biasing switch. The biasingswitch is selectively operable to adjust the operation of the at leasttwo wheels so that the mower can track a desired path. The biasingswitch sends signals to the microprocessor in response to operation ofthe biasing switch that the microprocessor uses to control the operationof the at least two wheels.

Optionally, the mower may further comprise a mode switch. The modeswitch is selectively operable between a work position and a transportposition to adjust the operation of the at least two wheels. The workposition corresponds to normal operation of the mower. The transportposition corresponds to high speed operation of the mower. The modeswitch sends a signal to the microprocessor that the microprocessor usesto control the operation of the at least two wheels. The microprocessoroperates the mower in a normal mode when the mode switch is in the workposition. The microprocessor reduces a rate at which the at least twowheels steer the mower when the mode switch is in the transport mode sothat the mower can be safely turned during high speed operation.

Optionally, the mower may further comprise a gain controller. The gaincontroller is selectively operable and allows a user of the mower toadjust the response of the mower caused by operation of the at least onecontroller. Operation of the gain controller causes the gain controllerto send signals to the microprocessor and inform the microprocessor onhow to interpret signals from the at least one controller. Themicroprocessor adjusts the operation of the at least two wheels inresponse to signals received by the microprocessor from the at least onecontroller based upon signals received from the gain controller.

In an alternate embodiment, the at least one controller furthercomprises a first and second controller. The first controller sendssignals to the microprocessor that the microprocessor uses to controlthe operation of a first wheel of the at least two wheels so that theoperation of the first controller causes the first wheel to rotate. Thesecond controller send signals to the microprocessor that themicroprocessor uses to control the operation of a second wheel of the atleast two wheels so that operation of the second controller causes thesecond wheel to rotate. Preferably, the first and second controllers areeach selectively movable between forward and reverse positions. Movementof the first controller toward the forward position causes the firstwheel to rotate in a direction that corresponds to propelling the mowerin a forward direction while movement of the first controller toward thereverse position causes the first wheel to rotate in a direction thatcorresponds to propelling the mower in a backward direction. Movement ofthe second controller toward the forward position causes the secondwheel to rotate in a direction that corresponds to propelling the mowerin a forward direction while movement of the second controller towardthe reverse position causes the second wheel to rotate in a directionthat corresponds to propelling the mower in a backward direction.

Preferably, each controller has a neutral position disposed between theforward and reverse positions. Positioning of the first and secondcontrollers in the neutral positions causes the respective first andsecond wheels to not be driven. Even more preferably, the first andsecond controllers are each biased to the neutral positions so that thefirst and second controllers return to the neutral positions when noforce is being applied to the first and second controllers. Optionally,but preferably, movement of the first and second controllers from theneutral positions toward the forward and reverse positions causes aspeed of rotation of the respective first and second wheels to increasein proportion to the movement of the first and second controllers fromthe neutral positions. Preferably, the proportional increase in thespeed of rotation of the at least two wheels in response to movement ofthe first and second controllers from the neutral positions toward theforward positions is greater than the proportional increase in the speedof rotation of the at least two wheels in response to movement of thefirst and second controllers from the neutral positions toward thereverse positions. The difference in the proportional increases in thespeed of rotation makes the mower capable of being propelled faster inthe forward direction than in the backward direction.

In a different alternate embodiment, the at least one controller furthercomprises first and second controllers. The first controller sendssignals to the microprocessor that the microprocessor uses to controlthe operation of the at least two wheels. The signals from the firstcontroller inform the microprocessor of whether the mower is to bepropelled in a forward or backward direction. The second controllersends signals to the microprocessor that the microprocessor uses tocontrol the operation of the at least two wheels. The signals from thesecond controller inform the microprocessor of a direction in which themower is to be steered. Preferably, the first and second controllers areselectively moveable. The first controller is selectively moveablebetween forward and reverse positions. Movement of the first controllertoward the forward position causes the at least two wheels to rotate ina direction that corresponds to propelling the mower in a forwarddirection. Movement of the first controller toward the reverse positioncauses the at least two wheels to rotate in a direction that correspondsto propelling the mower in a backward direction. The second controlleris selectively moveable between left and right positions. Movement ofthe second controller toward the left position causes the at least twowheels to rotate at different rates so that the mower turns to the left.Movement of the second controller toward the right position causes theat least two wheels to rotate at different rates so that the mower turnsto the right.

Preferably, the first controller has a neutral position disposed betweenthe forward and reverse positions. Positioning of the first controllerin the neutral position causes the at least two wheels to not be driven.Even more preferably, the first controller is biased to the neutralposition so that the first controller is positioned in the neutralposition when no force is being applied to the first controller.Movement of the first controller from the neutral position toward theforward and reverse positions causes a speed of rotation of the at leasttwo wheels to increase in proportion to the movement of the firstcontroller from the neutral position. The proportional increase in thespeed of rotation of the at least two wheels in response to movement ofthe first controller from the neutral position toward the forwardposition is greater than the proportional increase in the speed ofrotation of the at least two wheels in response to movement of the firstcontroller from the neutral position toward the reverse position. Thedifference in the proportional increases in response to movement of thefirst controller allows the mower to be propelled faster in the forwarddirection than in the backward direction.

The first controller can be a joystick that moves linearly between theforward and reverse positions. Alternatively, the first controller canbe a foot pedal that rotates about an axis between the forward andreverse positions.

Preferably, the second controller has a neutral position disposedbetween the left and right positions. Positioning of the secondcontroller in the neutral position causes the second controller to notaffect a rate at which each of the at least two wheels rotate. Even morepreferably, the second controller is biased to the neutral position sothat the second controller is positioned in the neutral position when noforce is being applied to the second controller. Movement of the secondcontroller from the neutral position toward the left and right positionscauses the difference in the rate of rotation of the at least two wheelsto increase in proportion to the movement of the second controller fromthe neutral position.

Optionally, but preferably, the second controller is selectivelymoveable between extreme left and extreme right positions. The extremeleft and extreme right positions are disposed beyond the respective leftand right positions so that the second controller must move past theleft and right positions to reach the respective extreme left andextreme right positions. Movement of the second controller past the leftposition toward the extreme left position causes the mower to countersteer left. Movement of the second controller past the right positiontoward the extreme right position causes the mower to counter steerright. Preferably, movement of the second controller past the left andright positions toward the respective extreme left and extreme rightpositions causes a speed of the counter steer to increase in proportionto the movement past the left and right positions. Preferably, movementof the second controller past the left and right positions toward therespective extreme left and extreme right positions provides a tactilesensation so that an operator of the mower will feel the tactilesensation prior to the mower counter steering.

The second controller can be a steering wheel that rotates. Rotation ofthe steering wheel causes the second controller to move between theextreme left and extreme right positions. Alternatively, the secondcontroller can be a joystick that moves linearly between the extremeleft and extreme right positions.

In an alternative embodiment, a drive-by-wire dual path hydraulicallydriven riding lawn mower comprises first and second hydraulic pumps. Thefirst and second hydraulic pumps provide respective first and secondflows of hydraulic fluid. There are first and second hydraulicallydriven wheels that operate independently and are capable ofbi-directional rotation. The first and second wheels are independentlyrotated by the respective first and second flows of hydraulic fluid. Theindependent rotation of the first and second wheels propel and steer themower. The microprocessor controls the operation of the first and secondwheels by controlling the first and second flows of hydraulic fluid tothe respective first and second wheels in accordance with signalsreceived by the microprocessor. At least one controller sends signals tothe microprocessor that the microprocessor uses to control the operationof the first and second wheels. The operation of the at least onecontroller causes the first and second wheels to propel and steer themower. Preferably, the mower further comprises first and secondproportional servo valves. The first and second valves control adirection and volume of flow of the respective first and second flows ofhydraulic fluid in response to signals received from the microprocessor.The controlling of the direction and volume of flow of the first andsecond flows of hydraulic fluid controls a direction and speed ofrotation of the respective first and second wheels.

Further areas of applicability of the present invention will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples, whileindicating the preferred embodiment of the invention, are intended forpurposes of illustration only and are not intended to limit the scope ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description and the accompanying drawings, wherein:

FIG. 1 is a perspective view of a zero turning radius vehicle, in theform of a drive-by-wire lawn mower, according to the principles of thepresent invention;

FIG. 2A is an enlarged partial view of the controllers of thedrive-by-wire lawn mower of FIG. 1;

FIG. 2B is an enlarged side elevation view of one of the controllers ofFIG. 2A along line 2B;

FIG. 2C is an enlarged partial view of an alternate embodiment for thecontrollers of the drive-by-wire lawn mower of FIG. 1;

FIG. 2D is an enlarged partial view of a different alternate embodimentfor the controllers of the drive-by-wire lawn mower of FIG. 1;

FIG. 3 is a plan view of the control panel of the drive-by-wire lawnmower of FIG. 1;

FIG. 4 is a simplified schematic diagram showing the hydraulic circuitand the electronic control circuit for the drive-by-wire lawn mower ofFIGS. 1 and 5;

FIG. 5 is an alternate embodiment of a drive-by-wire lawn mower of thepresent invention;

FIG. 6 is an enlarged partial view of the steering control for thedrive-by-wire lawn mower of FIG. 5; and

FIG. 7 is an enlarged partial view of the foot pedal controller of thedrive-by-wire lawn mower of FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of the preferred embodiment(s) is merelyexemplary in nature and is in no way intended to limit the invention,its application, or uses.

Referring to FIG. 1, there is shown a zero turning radius vehicle, inthe form of drive-by-wire riding lawn mower 20, in accordance with apreferred embodiment of the present invention. While the zero turningradius vehicle is illustrated and described as being a drive-by-wireriding lawn mower 20, it should be understood that the principles of thepresent invention are applicable to other zero turning radius vehicles,including but not limited to skid steer loaders, other turf carevehicles, and the like. Zero turning radius vehicles are generallydefined as vehicles having two or more wheels capable of independentbi-directional rotation so that the zero turning radius vehicle canperform counter steering operations. That is, the two or moreindependent wheels of a zero turning radius vehicle are capable of beingsimultaneously rotated in differing directions (i.e. one wheel rotatingclockwise while the other wheel rotates counter clockwise) so that thevehicle can execute a zero radius turn. Therefore, it should beunderstood that the principles of the invention can be applied to zeroturning radius vehicles that are not riding lawn mowers. The mower 20generally comprises a plurality of wheels 22, a mower deck 24, a seat26, a control panel 28, and one or more controllers 30. Referring now toFIG. 4, the mower 20 has an internal combustion engine 32 that providespower to the mower 20. The internal combustion engine 32 is aconventional internal combustion engine 32 and it has a horizontaloutput shaft 34. The output shaft 34 drives first and second hydraulicpumps 36, 38 in tandem. The first and second hydraulic pumps 36, 38 areswash plate pumps, as is known in the art. The first and secondhydraulic pumps 36, 38 have respective first and second proportionalservo valves 40, 42 which are electrically operated. The first andsecond valves 40, 42 control the swash plate (not shown) of therespective first and second hydraulic pumps 36, 38. The first and secondhydraulic pumps 36, 38 provide first and second flows of hydraulic fluid44, 46 to respective first and second hydraulic motors 48, 50. The firstand second hydraulic motors 48, 50 are connected to respective first andsecond hydraulically driven wheels 52, 54. The first and second drivenwheels 52, 54 operate independently of each other and are capable ofbi-directional rotation, as is known in the art. The direction ofrotation of the first and second driven wheels 52, 54 is dependent uponthe direction of flow of the respective first and second flows ofhydraulic fluid 44,46.

The first hydraulic pump 36 is connected to the first hydraulic motor 48by first and second hydraulic lines 56, 58. The first flow of hydraulicfluid 44 flows between the first hydraulic pump 36 and the firsthydraulic motor 48 via the first and second hydraulic lines 56, 58. Thesecond hydraulic pump 38 is connected to the second hydraulic motor 50by third and fourth hydraulic lines 60, 62. The second flow of hydraulicfluid 46 flows between the second hydraulic pump 38 and the secondhydraulic motor 50 via the third and fourth hydraulic lines 60, 62. Thefirst and second flows of hydraulic fluid 44, 46 can flow between therespective first and second hydraulic pumps 36, 38 and the respectivefirst and second hydraulic motors 48, 50 in any direction. That is, thefirst flow of hydraulic fluid 44 can flow from the first hydraulic pump36 to the first hydraulic motor 48 via the first hydraulic line 56 andreturn from the first hydraulic motor 48 to the first hydraulic pump 36via the second hydraulic line 58 or, conversely, the first flow ofhydraulic fluid 44 can flow from the first hydraulic pump 36 to thefirst hydraulic motor 48 via the second hydraulic line 58 and returnfrom the first hydraulic motor 48 to the first hydraulic pump 36 via thefirst hydraulic line 56. Likewise, the second flow of hydraulic fluid 46can flow from the second hydraulic pump 38 to the second hydraulic motor50 via the third hydraulic line 60 and return from the second hydraulicmotor 50 to the second hydraulic pump 38 via the fourth hydraulic line62 or, conversely, the second flow of hydraulic fluid 46 can flow fromthe second hydraulic pump 38 to the second hydraulic motor 50 via thefourth hydraulic line 62 and return from the second hydraulic motor 50to the second hydraulic pump 38 via the third hydraulic line 60. Thefirst and second hydraulic pumps 36, 38 are connected to a hydraulicfluid reservoir (not shown), as is known in the art.

The direction of flow of the first and second flows of hydraulic fluid44, 46 is dependent upon the position of the swash plates (not shown) inthe respective first and second hydraulic pumps 36, 38. As was mentionedabove, the first and second valves 40, 42 control the swash plates inthe respective first and second hydraulic pumps 36, 38. Therefore, thedirection of flow of the first and second flows of hydraulic fluid 44,46 are determined by the operation of the respective first and secondvalves 40, 42. When it is desired to rotate the first and/or seconddriven wheels 52, 54 in a direction that corresponds to propelling themower 20 in a forward direction, the first and/or second valves 40, 42adjust the swash plates in the respective first and/or second hydraulicpumps 36, 38 so that the first and/or second flows of hydraulic fluid44, 46 flow from the first and/or second hydraulic pumps 36, 38 to therespective first and/or second hydraulic motors 48, 50 via therespective first and/or third hydraulic lines 56, 60. When it is desiredto rotate the first and/or second driven wheels 52, 54 in a directioncorresponding to propelling the mower 20 in a backward direction, thefirst and/or second valves 40, 42 adjust the swash plate in therespective first and/or second hydraulic pumps 36, 38 so that the firstand/or second flows of hydraulic fluid 44, 46 flow from the respectivefirst and/or second hydraulic pumps 36, 38 to the respective firstand/or second hydraulic motors 48, 50 via the second and/or fourthhydraulic lines 58, 62. In this manner, the first and second valves 40,42 can control the direction of rotation of the respective first andsecond driven wheels 52, 54.

Along with controlling the direction of flow of the first and secondflows of hydraulic fluid 44, 46, the first and second valves 40, 42 alsocontrol the volume of flow of the respective first and second flows ofhydraulic fluid 44, 46 to the respective first and second hydraulicmotors 48, 50. The first and second valves 40, 42 can adjust the angleof the swash plates, as is known in the art, in the respective first andsecond hydraulic pumps 36, 38 to control the volume of flow of the firstand second flows of hydraulic fluid 44, 46 between a maximum volume thatcorresponds to the maximum angle of the swash plates to a zero volumewhich corresponds to a neutral position of the swash plates. The volumeof flow of the first and second flows of hydraulic fluid 44, 46determine the speed of rotation of the respective first and seconddriven wheels 52, 54. Therefore, the first and second valves 40, 42 cancontrol both the direction and speed of rotation of the respective firstand second driven wheels 52, 54.

The first and second valves 40, 42 can move the swash plates in therespective first and second pumps 36, 38 between a maximum forwardorientation wherein the first and second flows of hydraulic fluid 44, 46are maximum volumes of flow that rotate the respective first and seconddriven wheels 52, 54 in a direction corresponding to propelling themower 20 in a forward direction, a neutral orientation wherein the firstand second flows of hydraulic fluid 44, 46 are zero and the first andsecond driven wheels 52, 54 are not driven by the first and second flowsof hydraulic fluid 44, 46, and a maximum backward orientation whereinthe first and second flows of hydraulic fluid 44, 46 are maximum volumesof flow that rotate the respective first and second driven wheels 52, 54in a direction corresponding to propelling the mower 20 in a backwarddirection. Because the first and second valves 40, 42 can beindependently operated, the first and second valves 40, 42 provideindependent control of each of the driven wheels 52, 54 so that themower 20 can be propelled at a variety of speeds in a forward directionand at a variety of speeds in a backward direction. Additionally,because the first and second valves 40, 42 can independently adjust thevolume of flow of the respective first and second flows of hydraulicfluid 44, 46 to the respective first and second driven wheels 52 54, therespective first and second driven wheels 52, 54 can be caused to rotateat different speeds and the mower 20 can be steered. That is, by causingthe first and second driven wheels 52, 54 to rotate at different speeds,the mower 20 will be propelled in a direction toward the slower rotatingwheel. The independent operation of the first and second valves 40, 42can also allow the mower 20 to operate in a counter steering mode. Thecounter steering mode corresponds to the first and second driven wheels52, 54 being rotated in opposite directions so that the mower 20 canmake extremely sharp turns.

The mower 20 also has conventional safety features. For example, theseat 26 has a user present switch (not shown) which actuates only when asufficiently heavy object, such as a user of the mower 20, is sitting inthe seat 26. In addition, a typical mechanical brake (not shown) is alsoprovided. The brake can be used for parking the mower 20. For safetyreasons, the brake must be on when the engine 32 is started. The brakeand the user present switch are interconnected so that if the userpresent switch is not activated and the parking brake is off the engine32 will stop, as is known in the art.

The above described operation and capabilities of the mower 20 areconventional and well known in the art. It should be understood thatwhile the invention is shown in the figures and is discussed as being amower 20 that is propelled and steered by hydraulically driven wheels52, 54 it should be understood that other means of independently drivingthe first and second driven wheels 52, 54 can be employed withoutdeparting from the scope of the invention as defined by the claims. Forexample, the first and second driven wheels 52, 54 can be independentlydriven by DC motors whose operation can be controlled by the one or morecontrollers 30 and the control panel 28 and still be within the scope ofthe invention. Therefore, other means of independently driving the firstand second driven wheels 52, 54, as will be apparent to those skilled inthe art, can be employed and still be within the scope of the inventionas defined by the claims.

Referring now to FIG. 4, the first and second valves 40, 42 arecontrolled by a microprocessor 64. The microprocessor 64 sends signalsto the first and second valves 40, 42 that the first and second valves40, 42 use to control the operation of the swash plates in therespective first and second hydraulic pumps 36, 38. The microprocessor64 thereby controls the first and second flows of hydraulic fluid 44, 46to the respective first and second hydraulic motors 48, 50 so that themicroprocessor 64 can control the speed and direction of rotation of thefirst and second driven wheels 52, 54. The microprocessor 64 therebycontrols the direction in which the mower 20 is propelled and thesteering of the mower 20. The microprocessor 64 can be positioned on themower 20 in any convenient location.

The microprocessor 64 controls the operation of the mower 20 in responseto signals that the microprocessor 64 receives from various componentsof the mower 20. For example, the microprocessor 64 receives signalsfrom the one or more controllers 30, which are preferably first andsecond controllers 66, 68. Optionally, the mower 20 can also have one ormore biasing switch(es) 70, a mode switch 72 and a gain controller 74that send signals to the microprocessor 64 that the microprocessor 64uses to control the operation of the mower 20, as will be discussed inmore detail below.

The first and second controllers 66, 68, as can be seen in FIG. 1, arepositioned in front of the respective left and right arms 76, 78 of themower 20. The first and second controllers 66, 68 can then be easilyreached and operated by a user of the mower 20. In a preferredembodiment, as can be seen in FIG. 2A, the first and second controllers66, 68 are each independently selectively moveable between forward,neutral and reverse positions. The first controller 66 is used tocontrol the operation of the first driven wheel 52 and the secondcontroller 68 is used to control the operation of the second drivenwheel 54. The first and second controllers 66, 68 send signals to themicroprocessor 64 that vary depending upon the position of the first andsecond controllers 66, 68. That is, as the first and second controllers66, 68 are moved toward the forward position, the first and secondcontrollers 66, 68 independently send signals to the microprocessor 64that instructs the microprocessor 64 to cause the respective first andsecond driven wheels 52, 54 be rotated in a direction that correspondsto propelling the mower 20 in a forward direction. Conversely, when thefirst and second controllers 66, 68 are moved toward the reversedirection, the first and second controllers 66, 68 independently sendsignals to the microprocessor 64 that instruct the microprocessor 64 tocause the respective first and second driven wheels 52, 54 to rotate ina direction corresponding to propelling the mower 20 in a backwarddirection. When the first and second controllers 66, 68 are positionedin neutral positions the first and second controllers 66, 68independently send signals to the microprocessor 64 that instructs themicroprocessor 64 to not drive the first and second driven wheels 52, 54so that the mower 20 remains at rest. Preferably, the first and secondcontrollers 66, 68 are both biased to the neutral position so that if auser of the mower 20 releases the first and/or second controller 66, 68the microprocessor 64 ceases to cause the respective first and/or seconddriven wheels 52, 54 to be driven.

Preferably, the movement of the first and second controllers 66, 68 fromneutral positions toward the forward or reverse positions causes thespeed of rotation of the respective first and second driven wheels 52,54 to increase in proportion to the movement of the respective first andsecond controllers 66, 68 from the neutral positions. In this manner,the speed at which the first and second driven wheels 52, 54 rotate canbe controlled by the movement of the respective first and secondcontrollers 66, 68 from the neutral positions. Preferably, theproportional increase in the speed of rotation of the first and seconddriven wheels 52, 54 in response to the movement of the respective firstand second controllers 66, 68 from the neutral positions toward theforward positions is greater than the proportional increase in the speedof rotation of the first and second driven wheels 52, 54 in response tothe movement of the respective first and second controllers 66, 68 fromthe neutral positions toward the reverse positions. This enables themower 20 to be propelled faster in the forward direction than in thebackward direction. This is an added safety feature that prevents theoperation of the mower 20 in the backward direction at a high speed. Thespeed at which the mower 20 is propelled in either the forward orbackward directions can be independently set to not exceed predeterminedspeeds. The microprocessor 64 can be programmed to control the movementof the first and second valves 40, 42 in response to movement of therespective first and second controllers 66, 68 so that the maximummovement of the swash plates in the first and second hydraulic pumps 36,38 is limited. Limiting the maximum movement of the swash plates in thefirst and second hydraulic pumps 36, 38 limits the speed at which therespective first and second driven wheels 52, 54 are rotated. Themicroprocessor 64 thereby controls the speed at which the first andsecond driven wheels 52, 54 can rotate and the speed at which the mower20 is propelled.

As is known in the art, dual path hydraulically driven vehicles can havetracking problems. For example, when the first and second controllers66, 68 are in the same positions relative to the neutral positions, thefirst and second flows of hydraulic fluid 44, 46 may not be equal due tovariations in the first and second hydraulic pumps 36, 38 the first andsecond valves 40, 42 and/or the swash plates within the first and secondhydraulic pumps 36, 38. Therefore, the first and second driven wheels52, 54 may be rotating at different speeds when the first and secondcontrollers 66, 68 are in the same positions relative to the neutralpositions. In this situation, the mower 20 will have a tendency to steertoward the wheel that is rotating at the lower speed and not trackproperly. The tracking problem also occurs when the mower 20 is beingused on a hillside where the mower 20 will typically wish to go downhill. To compensate for this tracking problem, the first and/or secondcontrollers 66, 68 can be optionally provided with biasing switch(es)70. As can be seen in FIG. 2B, the biasing switch 70 rotates about apivot point 80. Preferably, the biasing switches have indicia thatindicate “+” and “−”. The movement of the biasing switch 70 toward the“+” or “−” directions fine tunes the gain adjustment or proportionalresponse in the microprocessor 64 in response to movement of the firstand second controllers 66, 68 from the neutral positions. In thismanner, if the first driven wheel 52 is rotating faster than the seconddriven wheel 54 when the first and second controllers 66, 68 are in thesame positions relative to the neutral positions, the biasing switch 70on the first controller 66 can be pivoted toward the “−” position untilthe first and second driven wheels 52, 54 are rotating at the same speedand the mower 20 is tracking properly or, alternatively, the biasingswitch 70 on the second controller 68 can be pivoted towards the “+”position and held there until the first and second driven wheels 52, 54are rotating at the same speed and the mower 20 is tracking properly.The fine tuning of the gain by pivoting of the biasing switches 70allows for fine tuning of the control of the mower 20 in response todifferent situations encountered by the mower 20 during its operation.The fine tuning of the gain can thereby be performed by operation of oneor more biasing switches 70. The mower 20 can, therefore, be providedwith a single biasing switch 70 or multiple biasing switches 70.Preferably, the biasing switch 70 is biased to return to a neutralposition when the user of a lawn mower 20 is no longer pivoting thebiasing switch 70 along the pivot point 80.

Preferably, the first and second controllers are joysticks. Thejoysticks used on the mower 20 are conventional and well known in theart. For example, the joy sticks can be joysticks sold by OEM Controls,Inc. such as the Digisensor. The joysticks send pulses that correspondto the positions of the joysticks to the microprocessor 64 thatmicroprocessor 64 uses to control the first and second driven wheels 52,54. Each joystick preferably has a spring return to center feature thatbiases the joystick to a neutral position. The sensing of the joystickin its central position is done by a micro-switch which is operated by acam. The switch is actuated anytime the joystick is in a position otherthan the central or neutral position. The spring return to centerfeature can be accomplished by a simple mechanical helical spring (notshown) that is mounted to the joystick. A weather boot 71 can also beprovided along the base of the joystick to prevent foul weather fromentering the mechanical components of the joysticks.

While the first and second controllers 66, 68 have been and willcontinue to be described as preferably being joysticks, it should beunderstood that the first and second controllers 66, 68 can take avariety of forms and still be within the scope of the invention asdefined by the claims. The variety of forms in which the first andsecond controllers 66, 68 can be configured will be apparent to thoseskilled in the art. For example, the first and second controllers 66, 68can be slides which slide along a radial path between forward andreverse positions and that send signals to the microprocessor 64indicating the position of the slide controllers relative to a neutralposition and still be within the scope of the invention. Therefore, thepresent invention should not be limited to the use of joysticks for thefirst and second controller 66, 68.

The mower 20 has a control panel 28 that is shown in FIG. 3. The controlpanel 28 has a variety of switches that control the function andoperation of the mower 20. A throttle 82 is located on the control panel28 that controls the speed at which the internal combustion engine 32operates. A key switch 84 is also located on the control panel 28 andturns the mower 20 on and off and also starts the mower 20. The PTOswitch 86 can be selectively operated to engage and disengage the PTO(not shown). The optionally provided gain controller 74 is also locatedon the control panel 28. The gain controller 74 is selectively rotatableto adjust the gain that the microprocessor 64 uses in responding tosignals received from the first and second controllers 66, 68. The gaincontroller 74 can be increased or decreased by selectively rotating thegain controller 74 in the direction indicated by the “+” and “−” indiciarespectively. The microprocessor 64 uses the input from the gaincontroller 74 to control the operation of the first and second drivenwheels 52, 54 in response to signals received from the respective firstand second controllers 66, 68. The adjustment of the gain controller 74thereby enables a user of the mower 20 to adjust the sensitivity of thefirst and second controllers 66, 68 so that a customized feel or settingcan be established for the user of the mower 20.

While the gain controller 74 is shown as being a rotatable controller,it should be understood that the gain controller 74 can take a varietyof forms, as will be apparent to those skilled in the art, and still bewithin the scope of the invention as defined by the claims. For example,the gain controller 74 can be a switch that pivots like the preferredembodiment for the biasing switch 70 and still be within the scope ofthe invention. It should be further understood that the gain controller74 does not need to be located on the control panel 28 to be within thescope of the invention. The gain controller 74 can be located in avariety of positions on the mower 20 and be within the scope of theinvention as defined by the claims. However, it is preferred that thegain controller 74 be located at a position on the mower 20 that iseasily accessible by a user of the mower 20 while the mower 20 is inoperation so that the gain controller 74 can be adjusted by a userduring the operation of the mower 20.

The optional mode switch 72 is also preferably located on the controlpanel 28. The mode switch 72 is selectively moveable between normal andtransport settings. The mode switch 72 sends signals to themicroprocessor 64 that the microprocessor 64 uses to control theoperation and steering of the mower 20. More specifically, when the modeswitch 72 is positioned in the normal position, the lawn mower 20functions as has been described above. However, when the mode switch 72is positioned in the transport position, the mower 20 is allowed totravel at a higher speed. When in the transport position, themicroprocessor 64 decreases the rate at which the mower 20 can besteered so that when the mower 20 is operating at high speed, the mowerdoes not suddenly steer in one direction or another in response tosignals received from the first and second controllers 66, 68 andpresent an unsafe or hazardous situation for a user of the mower 20. Inother words, when the mode switch 72 is in the transport position, themicroprocessor 64 prevents the mower 20 from making abrupt movementsthat may disrupt a user from his/her seated position on the mower 20 andprevent possible injury to the user.

The transport position corresponds to when it is desired to move themower 20 at a high speed from one location to another. It is notexpected that the mower 20 will be used to mow turf while being operatedin the transport mode. The transport position corresponds to allowingthe mower 20 to travel at a faster speed with less sensitive steeringthan in a normal mode. When the mower 20 is operated in the transportmode, the microprocessor can be programmed to prevent the mower 20 fromperforming a counter steering operation or to only allow a countersteering operation below a predetermined speed.

In an alternate preferred embodiment, the one or more controllers 30, ascan be seen in FIG. 2C, are first and second controllers 66′, 68′. Thefirst controller 66′ is preferably positioned adjacent the left arm 76of the mower 20 and the second controller 68′ is preferably positionedadjacent the right arm 78 of the mower 20. The first controller 66′sends signals to the microprocessor 64 that the microprocessor 64 usesto control the operation of the first and second driven wheels 52, 54.The signals from the first controller 66′ inform the microprocessor 64of whether the mower 20 is to be propelled in a forward or backwarddirection. The first controller 66′ is moveable between forward andreverse positions and has a neutral position interposed between theforward and reverse positions. Preferably, the controller 66′ is biasedtowards the neutral position so that when no force is being applied tothe first controller 66′ the first controller 66′ is in the neutralposition. Movement of the first controller 66′ toward the forwardposition causes the first and second driven wheels 52, 54 to rotate in adirection that corresponds to propelling the mower 20 in a forwarddirection and, conversely, movement of the first controller 66′ towardthe reverse position causes the first and second driven wheels 52, 54 torotate in a direction that corresponds to propelling the mower 20 in abackward direction. When the first controller 66′ is positioned in theneutral position, the first and second driven wheels 52, 54 are notdriven and the mower 20 is not propelled. Preferably, the firstcontroller 66′ is a joystick, as was discussed above.

Preferably, movement of the first controller 66′ from a neutral positiontoward the forward or reverse positions causes a speed of rotation ofthe first and second driven wheels 52, 54 to increase in proportion tothe movement of the first controller 66′ from the neutral position. Evenmore preferably, the proportional increase in the speed of rotation ofthe first and second driven wheels 52, 54 in response to movement of thefirst controller 66′ from the neutral position toward the forwardposition is greater than the proportional increase in the speed ofrotation of the first and second driven wheels 52, 54 in response tomovement of the first controller 66′ from the neutral position towardthe reverse position. The differences in the proportional increases inthe speed of rotation of the first and second driven wheels 52, 54 inresponse to the first controller 66′ being moved toward the forwardposition as opposed to the reverse position enables the mower 20 to bepropelled at a higher speed in the forward direction than in thebackward direction.

The steering of the mower 20 is performed by the second controller 68′.The second controller 68′ sends signals to the microprocessor 64 thatthe microprocessor 64 uses to control the operation of the first andsecond driven wheels 52, 54. The signals from the second controller 68′inform the microprocessor 64 of a direction in which the mower 20 is tobe steered. The second controller 68′ is selectively moveable betweenleft and right positions and has a neutral position interposed betweenthe left and right positions. Movement of the second controller 68′ fromthe neutral position toward the left position causes the first andsecond driven wheels 52, 54 to rotate at different rates so that themower 20 turns to the left and, conversely, movement of the secondcontroller 68′ from the neutral position toward the right positioncauses the first and second driven wheels 52, 54 to rotate at differentrates so that the mower 20 turns to the right. When the secondcontroller 68′ is positioned in the neutral position, the first andsecond driven wheels 52, 54 should rotate at the same rate so that themower 20 travels in a straight line. In order to compensate for trackingproblems that may be experienced by the mower 20, that were discussedabove, the second controller 68′ preferably has a biasing switch 70′that is selectively moveable between left and right positions. Movementof the biasing switch 70′ toward the left position causes themicroprocessor to adjust the valve controlling the flow of hydraulicfluid to the driven wheel on the left side of the mower 20 so that thedriven wheel on the left side of the mower rotates at a faster speed sothat the tracking of the mower 20 can be corrected. Conversely, when thebiasing switch 70′ is moved toward the right position, themicroprocessors 64 adjust the valve that controls the flow of hydraulicfluid to the driven wheel on the right side of the mower 20 so that thedriven wheel on the right side of the mower rotates at a faster speed sothat tracking of the mower 20 can be corrected. Because the flow ofhydraulic fluid to the driven wheels has a maximum volume, a situationmay occur wherein the volume of flow to one of the driven wheels cannotbe increased in response to movement of the biasing switch 70′. In thissituation, the microprocessor 64 instead of increasing the volume offlow to one of the driven wheels will decrease the volume of flow to theopposite driven wheel so that the tracking can be corrected. Forexample, when the biasing switch 70′ is moved towards the left positionand the flow of hydraulic fluid to the driven wheel on the left side ofthe mower 20 cannot be increased, the microprocessor 64 will adjust thevalve that controls the flow of hydraulic fluid to the driven wheel onthe right side of the mower so that the flow of hydraulic fluid to thedriven wheel on the right side of the mower is decreased and the drivenwheel on the right side of the mower rotates at a lower speed so thatthe tracking of the mower 20 can be corrected. The converse is also trueif the biasing switch 70′ were selectively moved to the right positionand the driven wheel on the right side of the mower was alreadyreceiving a maximum flow of hydraulic fluid. The biasing switch 70′ inconjunction with the microprocessor 64 thereby allow the tracking of themower 20 to be corrected by adjusting the volume of flow of thehydraulic fluid to the driven wheels.

Preferably, the second controller 68′ is biased to the neutral positionso that when no force is being applied to the second controller 68′, thesecond controller 68′ will be in the neutral position. Preferably, themovement of the second controller 68′ from the neutral position towardsthe right or left positions increases the speed at which the mower 20turns to the right or left respectively. That is, the movement of thesecond controller 68′ from the neutral position toward the left andright positions causes the difference in the rate of rotation of thefirst and second driven wheels 52, 54 to increase in proportion to themovement of the second controller 68′ from the neutral position.

Optionally, but preferably, the second controller 68′ is selectivelymoveable between extreme left and extreme right positions. The extremeleft position corresponds to the mower 20 counter steering to the left.The extreme right position corresponds to the mower 20 counter steeringto the right. The extreme left and extreme right positions are disposedbeyond the respective left and right positions so that the secondcontroller 68′ must move pass the left and right positions to reach therespective extreme left and extreme right positions. As can be seen inFIG. 2C, the extreme left position and the extreme right position areindicated by “CS” (counter steer) indicia to the left and right of the“L” and “R” indicia respectively. Movement of the second controller 68′pass the left position toward the extreme left position causes the mower20 to counter steer left and, conversely, movement of the secondcontroller 68′ pass the right position toward the extreme right positioncauses the mower 20 to counter steer right.

Preferably, the movement of the second controller 68′ pass the left andright positions toward the respective extreme left and extreme rightpositions causes a speed of the counter steering to increase inproportion to the movement of the second controller 68′ pass the leftand right positions. Optionally, but preferably, the second controller68′ provides a tactile sensation to a user of the mower 20 when thesecond controller 68′ is moving pass the left or right positions andinto a counter steering operation. The tactile sensation provides awarning for the user of the mower 20 prior the mower 20 performing acounter steering operation so that the user can be prepared for thecounter steering operation of the mower 20. The tactile sensation can beprovided in a variety of ways, as will be apparent to those skilled inthe art. For example, the second controller 68′ can be a force feed backcontroller or joystick and the microprocessor 64 provides feed back tothe second controller 68′ that changes resistance to movement of thesecond controller 68′ pass the left and right positions. Cammed surfacescan also be used along with a retaining mechanism such as a spring orelastomeric material that increases the resistance to movement of thesecond controller 68′ as the second controller 68′ passes the right orleft positions. Optionally, a tactile sensation can be provided for theentire range of motion of the second controller 68′ with a marked changein the tactile sensation occurring prior to the movement of the secondcontroller 68′ into a counter steering position. Preferably, the secondcontroller 68′ is a joystick that moves linearly between the extremeleft and extreme right positions. However, as was discussed above, thesecond controller 68′ can come in a variety of forms and still be withinthe scope of the invention as defined by the claims.

In a different alternate embodiment, as shown in FIGS. 5, the mower 20has first and second controllers 66″, 68″ that operate in a similarmanner as the first and second controllers 66′, 68′. In this embodiment,the first controller 66″, as can be seen in FIG. 7, is a foot pedal 88that can be operated by a foot of the user of the mower 20 and instructsthe microprocessor 64 of whether to propel the mower 20 in a forward orbackward direction, and the second controller 68″, as can be seen inFIG. 6, is a steering wheel 90 that instructs the microprocessor 64 ofthe direction in which to steer the mower 20.

The foot pedal 88 pivots about an axis 92 between forward and reversepositions. A neutral position is interposed between the forward andreverse positions and, preferably, the foot pedal 88 is biased so thatthe foot pedal 88 is in the neutral position when no force is beingexerted on the foot pedal 88. Operation of the foot pedal 88 isidentical to operation of the first controller 66′, discussed above, theonly difference being that the foot pedal 88 is rotated about a pivotaxis 92 between the forward and reverse positions while the firstcontroller 66′ was moved linearly between the forward and reversepositions. In other words, rotation of the foot pedal 88 toward theforward position sends signals to the microprocessor 64 that instructthe microprocessor 64 to drive the first and second driven wheels 52, 54in a direction that corresponds to propelling the mower 20 in a forwarddirection and, conversely, the pivoting of the foot pedal 88 toward thereverse position causes the foot pedal 88 to send signals tomicroprocessor 64 that instruct the microprocessor 64 to drive the firstand second driven wheels 52, 54 in a direction that corresponds topropelling the mower 20 in a backward direction. Like the firstcontroller 66′, movement of the foot pedal 88 from the neutral positiontoward the forward and reverse positions causes a proportional increasein the speed of rotation of the first and second driven wheels 52, 54 inresponse to movement of the foot pedal 88 from the neutral positiontoward the forward and reverse positions. Additionally, the proportionalincrease in the speed of rotation of the first and second wheels 52, 54is larger as the foot pedal 88 pivots toward the forward position thenwhen the foot pedal 88 pivots toward the reverse position so that themower 20 is capable of being propelled faster in the forward directionthen in the backward direction.

The steering wheel 90 rotates between left and right positions with aneutral position interposed between the left and right positions. Theoperation of steering wheel 90 is very similar to the operation of thesecond controller 68′ with a difference being that the steering wheel 90rotates between positions while the second controller 68′ moved linearlybetween positions. The steering wheel 90 has a sensor (not shown) thatinforms the microprocessor 64 of the position of the steering wheel 90,as is known in the art. Rotation of the steering wheel 90 from theneutral position and toward the left position causes the first andsecond driven wheels 52, 54 to rotate at different rates so that themower turns to the left and, conversely, rotation of the steering wheel90 from the neutral position and toward the right position causes thefirst and second driven wheels 52, 54 to rotate at different rates sothat the mower turns to the right. Preferably, the steering wheel 90 isbiased to return to the neutral position so that when no force isapplied to the steering wheel 90, the mower 20 will move in a straightdirection when being propelled.

Preferably, rotation of the steering wheel 90 from the neutral positiontoward the left and right positions causes the difference in the rate ofrotation of the first and second driven wheels 52, 54 to increase inproportion to the rotation of the steering wheel 90 from the neutralposition. Even more preferably, the steering wheel 90 can be selectivelyrotated between extreme left and extreme right positions that aredisposed beyond the respective left and right positions so that thesteering wheel 90 must move pass the left and right positions to reachthe respective extreme left and extreme right positions. Rotation of thesteering wheel 90 pass the left position toward the extreme leftposition causes the mower 20 to counter steer to the left and,conversely, rotation of the steering wheel 90 pass the right positiontoward the extreme right position causes the mower 20 to counter steerto the right. Preferably, the rotation of the steering wheel 90 pass theleft and right positions toward the respective extreme left and extremeright positions causes a speed of the counter steer to increase inproportion to the rotation of the steering wheel 90 pass the left andright positions.

As was discussed above with respect to the second controller 68′, thesteering wheel 90 preferably provides a tactile sensation to a user ofthe mower 20 when the steering wheel 90 is rotated pass the left andright positions so that a user of the mower 20 will feel the tactilesensation prior to the mower 20 performing a counter steering operation.The tactile sensation can be provided by a variety of ways, as will beapparent to those skilled in the art. For example, the steering wheel 90can have detents that are positioned along the range of rotation of thesteering wheel 90 so that when the steering wheel 90 enters a specificposition, the user of the mower 20 feels a change in the effort requiredto rotate the steering wheel 90. A cammed surface can be provided sothat as the steering wheel 90 is rotated off center (away from theneutral position), the resistance to rotation of the steering wheel 90is increased and the effort required to rotate the steering wheel 90increases. When the rotation of the steering wheel 90 gets to the end ofthe left and right positions, the cammed surface can have a larger angleso that the force required to further rotate steering wheel 90 isfurther increased in the counter steering region. If the increase in thesteering force required to rotate the steering wheel 90 is significantlylarge enough, the change from steering left or right to counter steeringleft or counter steering right will be easily discernable to a user ofthe mower 20.

Optionally, the steering wheel 90, like the second controller 68′, canbe provided with one of more biasing switches 70″. The one or morebiasing switches 70″ can be positioned on spokes 94 of the steeringwheel 90. The biasing switches 70″ can be selectively operated by a userof the mower 20. The biasing switches 70″, as was discussed above,provide signals to the microprocessor 64 that the microprocessor 64 usesto fine tune the control of the first and second driven wheels 52, 54 sothat the mower 20 can track a desired path. The steering wheel 90 canhave two biasing switches 70″ to separately fine tune the control of thefirst and second driven wheels 52, 54. For example, the biasing switch70″ located on the right side of the steering wheel 90 can be configuredto fine tune the operation of the driven wheel on the right side of themower 20 in response to rotation of the steering wheel 90 toward theright position and the biasing switch 70″ located on the left side ofthe steering wheel 90 can be configured to fine tune the operation ofthe driven wheel on the left side of the mower 20 in response torotation of the steering wheel 90 toward the left position. That is, theoperation of the biasing switches 70″ adjusts how the microprocessor 64controls the operation of the first and second valves 40, 42 in responseto the position of the steering wheel 90. The operation of the biasingswitches 70″ thereby allows the mower 20 to be adjusted so that themower 20 can properly track a desired path. Optionally, the biasingswitches 70″ can be a single biasing switch 70″ that functions identicalto the biasing switch 70′ discussed above in relation to the secondcontroller 68′.

The steering wheel 90 can be positioned on the mower 20 in a variety oflocations. For example, as shown in FIG. 5, the steering wheel 90 can bemounted on a pedestal 96 that is positioned between the legs of a useron the mower 20, as is known in the art. Optionally, the steering wheel90 can be on a plate (not shown) having a hinge that allows the steeringwheel 90 to be mounted next to one of the arms 76, 78 of the mower 20and to be selectively flipped up and down in front of a user seated inthe seat 26 of mower 20. Because the steering wheel 90 is notmechanically linked to the wheels 22 of the mower 20, the steering wheel90 can be positioned in a variety of manners and in a variety oflocations that are convenient for the user of the mower 20.

In a different preferred embodiment, the one or more controllers 30comprises a single controller 98 as shown in FIG. 2D. The singlecontroller 98 is selectively moveable in two axes and sends signals tothe microprocessor 64 that the microprocessor 64 uses to control theoperation of the first and second driven wheels 52, 54. Movement of thesingle controller 98 along a first axis 100 corresponds to instructingthe microprocessor 64 to control the operation of the first and seconddriven wheels 52, 54 so that the mower 20 is propelled in a forward orbackward direction. Movement of the single controller 98 along a secondaxis 102 corresponds to instructing the microprocessor 64 to control theoperation of the first and second driven wheels 52, 54 so that the mower20 steers to the left or right. Movement of the single controller 98along the first and second axes 100, 102 provides a range of movementalong a plane in which the single controller 98 can be positioned.Movement of the single controller 98 along the plane corresponds todesired operation of the mower 20. The single controller 98 providessignals to the microprocessor 64 that informs the microprocessor 64 ofthe location of the single controller 98 within the plane. The plane isdivided into areas that correspond to different operations of the mower20. The operation of the mower 20 in response to the location of thesingle controller 98 within the plane is programmed into themicroprocessor 64. Preferably, movement of the single controller 98linearly along the first axis 100 will cause the mower 20 to bepropelled in either a forward or backward direction. If the singlecontroller 98 deviates from traveling linearly along the first axis 100so that the single controller 98 travels along the second axis 102, themower 20 will perform a steering operation along with being propelled ineither the forward or reverse direction. If the single controller 98 ismoved along the second axis 102 a sufficient distance, the mower 20 willperform a counter steering operation to the left or right. Optionally,but preferably, the single controller 98 can also be provided with abiasing switch that is identical to the biasing switch 70′ on the secondcontroller 68′. The biasing switch 70′ on the single controller 98enables a user of the lawn mower 20 to fine tune the operation of thefirst and second driven wheels 52, 54 so that the mower 20 can properlytrack a desired path. The boundaries of the predetermined positions ofthe single controller 98 that instruct the microprocessor 64 whether topropel the mower in a forward, backward, steer right, steer left,counter steer right or counter steer left operation can be adjusted byprogramming the microprocessor 64. This enables a user of the mower 20to customize the operation of the single controller 98 to meetindividual preferences.

The one or more controllers 30 can communicate with the microprocessor64 in a variety of manners. Preferably, the one or more controllers 30are connected to the microprocessor 64 by electrical wires (not shown).The use of electrical wires to connect the one or more controllers 30 tothe microprocessor 64 eliminates the need for complex mechanicallinkages to control the operation of the mower 20. The use of electricalwires also facilitate the mounting of the one or more controllers 30 inlocations that are convenient to the user of the mower 20. Optionally,the one or more controllers 30 can communicate with the microprocessor64 via wireless communication such as by RF signals, infrared signalsand other ways that will be apparent to those skilled in the art.Therefore, the one or more controllers 30 can be connected to themicroprocessor 64 by a variety of means and still be within the scope ofthe invention as defined by the claims.

The specific one or more controllers 30 that are used on the mower 20can be varied to meet the needs of a user of the mower 20. For example,the first controllers 66′, 66″ are generally interchangeable and can beused with either of the second controllers 68′, 68″. Likewise, thesecond controllers 68′, 68″ are also interchangeable and can be usedwith either of the first controllers 66′, 66″. The mower 20 can have acombination of first and second controllers such that a user 20 isprovided with numerous and redundant ways of controlling the operationof the mower 20. For example, the mower 20 can be provided with thefirst and second controllers 66, 68 along with the first and secondcontroller 66″, 68″ or can be provided with a single controller 98 alongwith the first and second controllers 66″, 68″ to provide a user of themower 20 with various options on how to control the operation of themower 20. It should be understood that the above examples are forillustrative purposes only and that the above described controllers canbe combined in a variety of ways that go beyond those illustrated anddiscussed and that will be apparent to those skilled in the art andstill be within the scope of the invention as defined by the claims.Therefore, the combination of the one or more controllers 30 should notbe limited to those specifically used as illustrating the possibilitiesof combining the various one or more controllers 30.

The flexibility and variety in which the one or more controllers 30 canbe provided on the mower 20 enables a person to customize the mower 20and also allows the mower 20 to be operated by a person that isphysically handicapped. For example, if the user of the mower 20 hasonly a single arm, the mower 20 can be provided with the foot pedal 88and the steering wheel 90 or with the single controller 98 so that thesingle armed user can operate the mower 20. If the user does not haveany legs, the mower 20 can be provided with the first and secondcontroller 66, 68 or 66′, 68′ or 66′, 68″ or a single controller 98 sothat the legless user can operate the mower 20.

The microprocessor 64 can be programmed to control the operation of thefirst and second driven wheels 52, 54 so that the mower 20 can be safelyoperated and prevented from injuring any turf on which the mower 20 isoperated. Preferably, the microprocessor 64 controls the accelerationand deceleration of the first and second driven wheels 52, 54 inresponse to signals received from the one or more controllers 30 in acontrolled manner that prevents abrupt movement of the mower 20 thatcould upset a user riding on the mower 20 or cause an overload conditionto exist on the turf which will cause one or more of the wheels 22 onthe mower 20 to injure the turf. For example, when the one or morecontrollers 30 instruct the microprocessor 64 to perform a countersteering operation, the microprocessor 64 will start by slowing down themower 20 and allowing one of the first or second driven wheels 52, 54 tocontinue to rotate forwardly while the opposite first or second drivenwheel 52, 54 slows down, stops and goes into reverse. In order to avoidsudden and unexpected accelerations upon the mower 20 or the user of themower 20, this is a controlled deceleration of the first or seconddriven wheel 52, 54 to its stopped position and then a controlledacceleration of the first or second driven wheel 52, 54. Because thefirst or second driven wheel 52, 54 is now going in reverse, it willnever be allowed to go as fast as the opposite first or second drivenwheel 52, 54 that is going in a forward direction. By controlling thedeceleration and acceleration of the first or second driven wheels 52,54 in the counter steering situation, the mower 20 not only avoidssudden maneuvers which might catch the user of the mower 20 off guard,but the turf underneath the first or second driven wheels 52, 54 is notsubjected to overload forces which could easily result in the corrugatedtread on the first or second driven wheels 52, 54 tearing up the turfunderfoot, particularly when the turf is wet. The microprocessor 64thereby provides for the safe control and operation of the mower 20along with preventing a counter steering operation from causing overloadforces to act on the turf on which the mower 20 is operating.

The programming of the microprocessor 64 can be provided by a controlbox (not shown). It can have a display that enables various thresholds,set points and gains to be programmed into the microprocessor 64. Anysuitable control box may be utilized, as will be apparent to thoseskilled in the art. For example, the OPTIMIZER unit from OEM Controls,Inc. can be used to control the operation and programming of themicroprocessor 64. The use of a control box enables the control andoperation of the mower 20 to be customized by the user of the mower 20.

The description of the invention is merely exemplary in nature and,thus, variations that do not depart from the gist of the invention areintended to be within the scope of the invention. Such variations arenot to be regarded as a departure from the spirit and scope of theinvention.

1. A drive-by-wire dual path hydraulically driven riding lawn mower, themower comprising: first and second hydraulic pumps, the first and secondhydraulic pumps providing respective first and second flows of hydraulicfluid; first and second hydraulically driven wheels that operateindependently and are capable of bi-directional rotation, the first andsecond wheels being independently rotated by the respective first andsecond flows of hydraulic fluid, and the independent rotation of thefirst and second wheels propelling and steering the mower; amicroprocessor, the microprocessor controlling the operation of thefirst and second wheels by controlling the first and second flows ofhydraulic fluid to the respective first and second wheels in accordancewith signals received by the microprocessor; at least one controller,the at least one controller sending signals to the microprocessor thatthe microprocessor uses to control the operation of the first and secondwheels so that operation of the at least one controller causes the firstand second wheels to propel and steer the mower; and first and secondproportional servo valves, the first and second valves controlling adirection and volume of flow of the respective first and second flows ofhydraulic fluid in response to signals received from the microprocessor,the controlling of the direction and volume of flow of the first andsecond flows of hydraulic fluid controlling a direction and speed ofrotation of the respective first and second wheels; wherein the at leastone controller further includes: a first controller that sends signalsto the microprocessor that the microprocessor uses to control theoperation of the first and second wheels, the signals from the firstcontroller informing the microprocessor of whether the mower is to bepropelled in a forward or backward direction; and a second controllerthat sends signals to the microprocessor that the microprocessor uses tocontrol the operation of the first and second wheels, the signals fromthe second controller informing the microprocessor of a direction inwhich the mower is to be steered.
 2. The mower of claim 1, wherein: thefirst controller is selectively moveable between forward and reversepositions and wherein movement of the first controller toward theforward position causing the first and second wheels to rotate in adirection that corresponds to propelling the mower in a forwarddirection and movement of the first controller toward the reverseposition causing the first and second wheels to rotate in a directionthat corresponds to propelling the mower in a backward direction; thesecond controller is selectively moveable between left and rightpositions and wherein movement of the second controller toward the leftposition causing the first and second wheels to rotate at differentspeeds so that the mower turns to the left and movement of the secondcontroller toward the right position causing the first and second wheelsto rotate at different speeds so that the mower turns to the right. 3.The mower of claim 2, wherein the first controller has a neutralposition disposed between the forward and reverse positions andpositioning of the first controller in the neutral position causes thefirst and second wheels to not be driven.
 4. The mower of claim 3,wherein the first controller is biased to the neutral position so thatthe first controller is positioned in the neutral position when no forceis being applied to the first controller.
 5. The mower of claim 3,wherein movement of the first controller from the neutral positiontoward the forward and reverse positions causes the speed of rotation ofthe first and second wheels to increase in proportion to the movement ofthe first controller from the neutral position.
 6. The mower of claim 5,wherein the proportional increase in the speed of rotation of the firstand second wheels in response to movement of the first controller fromthe neutral position toward the forward position is greater than theproportional increase in the speed of rotation of the first and secondwheels in response to movement of the first controller from the neutralposition toward the reverse position so that the mower is capable ofbeing propelled faster in the forward direction than in the backwarddirection.
 7. The mower of claim 3, wherein the first controller is ajoystick that moves linearly between the forward and reverse positions.8. The mower of claim 3, wherein the first controller is a foot pedalthat rotates about an axis between the forward and reverse positions. 9.The mower of claim 2, wherein the second controller has a neutralposition disposed between the left and right positions and positioningof the second controller in the neutral position causes the secondcontroller to not effect the speed at which each of the first and secondwheels rotate.
 10. The mower of claim 9, wherein the second controlleris biased to the neutral position so that the second controller ispositioned in the neutral position when no force is being applied to thesecond controller.
 11. The mower of claim 9, wherein movement of thesecond controller from the neutral position toward the left and rightpositions causes a difference in the speed of rotation of the first andsecond wheels to increase in proportion to the movement of the secondcontroller from the neutral position.
 12. The mower of claim 9, whereinthe second controller is selectively moveable between extreme left andextreme right positions, the extreme left and extreme right positionsbeing disposed beyond the respective left and right positions so thatthe second controller must move past the left and right positions toreach the respective extreme left and extreme right position andmovement of the second controller past the left position toward theextreme left position causes the mower to counter steer left andmovement of the second controller past the right position toward theextreme right position causes the mower to counter steer right.
 13. Themower of claim 12, wherein movement of the second controller past theleft and right positions toward the respective extreme left and extremeright positions causes a speed of the counter steer to increase inproportion to the movement of the second controller past the left andright positions.
 14. The mower of claim 12, wherein movement of thesecond controller past the left and right positions toward therespective extreme left and extreme right positions provides a tactilesensation so that an operator of the mower will feel the tactilesensation prior to the mower counter steering.
 15. The mower of claim12, wherein the second controller is a steering wheel that rotates androtation of the steering wheel causes the second controller to movebetween the extreme left and extreme right positions.
 16. The mower ofclaim 12, wherein the second controller is a joystick that moveslinearly between the extreme left and extreme right positions.
 17. Adrive-by-wire dual path hydraulically driven riding lawn mower, themower comprising: first and second hydraulic pumps, the first and secondhydraulic pumps providing respective first and second flows of hydraulicfluid; first and second hydraulically driven wheels that operateindependently and are capable of bi-directional rotation, the first andsecond wheels being independently rotated by the respective first andsecond flows of hydraulic fluid, and the independent rotation of thefirst and second wheels propelling and steering the mower; amicroprocessor, the microprocessor controlling the operation of thefirst and second wheels by controlling the first and second flows ofhydraulic fluid to the respective first and second wheels in accordancewith signals received by the microprocessor; at least one controller,the at least one controller sending signals to the microprocessor thatthe microprocessor uses to control the operation of the first and secondwheels so that operation of the at least one controller causes the firstand second wheels to propel and steer the mower; and first and secondvalves, the first and second valves controlling a direction and volumeof flow of the respective first and second flows of hydraulic fluid inresponse to signals received from the microprocessor, the controlling ofthe direction and volume of flow of the first and second flows ofhydraulic fluid controlling a direction and speed of rotation of therespective first and second wheels.
 18. The mower of claim 17 furthercomprising a first controller that sends signals to the microprocessorthat the microprocessor uses to control the operation of the first andsecond wheels, the signals from the first controller informing themicroprocessor of whether the mower is to be propelled in a forward orbackward direction; and a second controller that sends signals to themicroprocessor that the microprocessor uses to control the operation ofthe first and second wheels, the signals from the second controllerinforming the microprocessor of a direction in which the mower is to besteered.
 19. The mower of claim 18, wherein: the first controller isselectively moveable between forward and reverse positions, whereinmovement of the first controller toward the forward position causing thefirst and second wheels to rotate in a direction that corresponds topropelling the mower in a forward direction and movement of the firstcontroller toward the reverse position causing the first and secondwheels to rotate in a direction that corresponds to propelling the mowerin a backward direction; and the second controller is selectivelymoveable between left and right positions, wherein movement of thesecond controller toward the left position causing the first and secondwheels to rotate at different speeds so that the mower turns to the leftand movement of the second controller toward the right position causingthe first and second wheels to rotate at different speeds so that themower turns to the right.
 20. The mower of claim 17, wherein: the firstcontroller has a neutral position disposed between the forward andreverse positions; and positioning of the first controller in theneutral position causes the first and second wheels to not be driven.21. The mower of claim 20, wherein the first controller is biased to theneutral position so that the first controller is positioned in theneutral position when no force is being applied to the first controller.22. The mower of claim 20, wherein movement of the first controller fromthe neutral position toward the forward and reverse positions causes thespeed of rotation of the first and second wheels to increase inproportion to the movement of the first controller from the neutralposition.
 23. The mower of claim 22, wherein the proportional increasein the speed of rotation of the first and second wheels in response tomovement of the first controller from the neutral position toward theforward position is greater than the proportional increase in the speedof rotation of the first and second wheels in response to movement ofthe first controller from the neutral position toward the reverseposition so that the mower is capable of being propelled faster in theforward direction than in the backward direction.
 24. The mower of claim17, wherein the first controller is a joystick that moves linearlybetween the forward and reverse positions.
 25. The mower of claim 17,wherein the first controller is a foot pedal that rotates about an axisbetween the forward and reverse positions.
 26. The mower of claim 18,wherein the second controller has a neutral position disposed betweenthe left and right positions and positioning of the second controller inthe neutral position causes the second controller to not effect thespeed at which each of the first and second wheels rotate.
 27. The mowerof claim 26, wherein the second controller is biased to the neutralposition so that the second controller is positioned in the neutralposition when no force is being applied to the second controller. 28.The mower of claim 26, wherein movement of the second controller fromthe neutral position toward the left and right positions causes adifference in the speed of rotation of the first and second wheels toincrease in proportion to the movement of the second controller from theneutral position.
 29. The mower of claim 26, wherein the secondcontroller is selectively moveable between extreme left and extremeright positions, the extreme left and extreme right positions beingdisposed beyond the respective left and right positions so that thesecond controller must move past the left and right positions to reachthe respective extreme left and extreme right positions and movement ofthe second controller past the left position toward the extreme leftposition causes the mower to counter steer left and movement of thesecond controller past the right position toward the extreme rightposition causes the mower to counter steer right.
 30. The mower of claim29, wherein movement of the second controller past the left and rightpositions toward the respective extreme left and extreme right positionscauses a speed of the counter steer to increase in proportion to themovement of the second controller past the left and right positions. 31.The mower of claim 29, wherein movement of the second controller pastthe left and right positions toward the respective extreme left andextreme right positions provides a tactile sensation so that an operatorof the mower will feel the tactile sensation prior to the mower countersteering.
 32. The mower of claim 29, wherein the second controller is asteering wheel that rotates and rotation of the steering wheel causesthe second controller to move between the extreme left and extreme rightpositions.
 33. The mower of claim 29, wherein the second controller is ajoystick that moves linearly between the extreme left and extreme rightpositions.